linux: Synchronize access to FontRenderParams cache.

Also clean up cache-clearing (used by tests).

BUG=401993

Review URL: https://codereview.chromium.org/458593002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288855 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 33 insertions, 16 deletions

diff --git a/ui/gfx/font_render_params_linux.cc b/ui/gfx/font_render_params_linux.cc
index 507c793..f02636e 100644
--- a/ui/gfx/font_render_params_linux.cc
+++ b/ui/gfx/font_render_params_linux.cc
@@ -7,10 +7,12 @@
 #include "base/command_line.h"
 #include "base/containers/mru_cache.h"
 #include "base/hash.h"
+#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "base/synchronization/lock.h"
 #include "ui/gfx/font.h"
 #include "ui/gfx/linux_font_delegate.h"
 #include "ui/gfx/switches.h"
@@ -21,12 +23,25 @@ namespace gfx {
 
 namespace {
 
-// Should cache entries by dropped by the next call to GetFontRenderParams()?
-// Used for tests.
-bool g_clear_cache_for_test = false;
+// Keyed by hashes of FontRenderParamQuery structs from
+// HashFontRenderParamsQuery().
+typedef base::MRUCache<uint32, FontRenderParams> Cache;
 
 // Number of recent GetFontRenderParams() results to cache.
-const size_t kCacheSize = 10;
+const size_t kCacheSize = 20;
+
+// A cache and the lock that must be held while accessing it.
+// GetFontRenderParams() is called by both the UI thread and the sandbox IPC
+// thread.
+struct SynchronizedCache {
+  SynchronizedCache() : cache(kCacheSize) {}
+
+  base::Lock lock;
+  Cache cache;
+};
+
+base::LazyInstance<SynchronizedCache>::Leaky g_synchronized_cache =
+    LAZY_INSTANCE_INITIALIZER;
 
 // Converts Fontconfig FC_HINT_STYLE to FontRenderParams::Hinting.
 FontRenderParams::Hinting ConvertFontconfigHintStyle(int hint_style) {
@@ -138,20 +153,14 @@ uint32 HashFontRenderParamsQuery(const FontRenderParamsQuery& query) {
 
 FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
                                      std::string* family_out) {
-  typedef base::MRUCache<uint32, FontRenderParams> Cache;
-  CR_DEFINE_STATIC_LOCAL(Cache, cache, (kCacheSize));
-
-  if (g_clear_cache_for_test) {
-    cache.Clear();
-    g_clear_cache_for_test = false;
-  }
-
   const uint32 hash = HashFontRenderParamsQuery(query);
   if (!family_out) {
     // The family returned by Fontconfig isn't part of FontRenderParams, so we
     // can only return a value from the cache if it wasn't requested.
-    Cache::const_iterator it = cache.Get(hash);
-    if (it != cache.end()) {
+    SynchronizedCache* synchronized_cache = g_synchronized_cache.Pointer();
+    base::AutoLock lock(synchronized_cache->lock);
+    Cache::const_iterator it = synchronized_cache->cache.Get(hash);
+    if (it != synchronized_cache->cache.end()) {
       DVLOG(1) << "Returning cached params for " << hash;
       return it->second;
     }
@@ -192,12 +201,20 @@ FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
   if (family_out && family_out->empty() && !query.families.empty())
     *family_out = query.families[0];
 
-  cache.Put(hash, params);
+  // Store the computed struct. It's fine if this overwrites a struct that was
+  // cached by a different thread in the meantime; the values should be
+  // identical.
+  SynchronizedCache* synchronized_cache = g_synchronized_cache.Pointer();
+  base::AutoLock lock(synchronized_cache->lock);
+  synchronized_cache->cache.Put(hash, params);
+
   return params;
 }
 
 void ClearFontRenderParamsCacheForTest() {
-  g_clear_cache_for_test = true;
+  SynchronizedCache* synchronized_cache = g_synchronized_cache.Pointer();
+  base::AutoLock lock(synchronized_cache->lock);
+  synchronized_cache->cache.Clear();
 }
 
 }  // namespace gfx